Switch-type near-infrared fluorescent probes for Hg2+ based on rhodamines

Mercury usually exists in the form of simple substances or Hg2+ in nature. Hg2+ is a highly toxic chemical that can easily cause great harm to the human body. It was very important to explore an efficient and stable method for detecting mercury ions. We designed and synthesized the near-infrared fluorescence sensor RBLY by using the good fluorescence response platform of rhodamine dye. Compared to traditional rhodamine dyes, its emission wavelength is red-shifted to 695 nm. Spectral experiments verified that it has the advantages of fast response and high selectivity to Hg2+. With the addition of S2-, the probe can exhibit fluorescence quenching behavior and reach a reversible equilibrium. The limit of detection is as low as 0.34 μM and the binding constant is 1.63 × 105 M−1. Besides, in the actual environmental water sample, a higher recovery rate is obtained. We also made relevant applications in the field of biology, where the probe RBLY have been successfully applied to living cells, plant cells and living bodies.